I took my truck for a long drive the other day and I noticed that the transmission was slipping. It was an intermittent problem and did not seem to be load dependent.
At one point I had cruise control on and when I noticed the slippage I tapped it down one without it locking, tapped it down once more, same thing, and finally, when I tapped it down a third time it locked up.
Mind you, when it is locked I can give it about 1/3 throttle without it slipping, so it is not a matter of exceeding the holding ability.
I tried putting it in third and it does the same thing, so I don't think it is the transmission, but the lockup clutch in the torque converter.
The fluid looked okay, but I didn't get a really good look at it. The level is perfect.
It is time to do a fluid change, since it has about 90,000 miles now, and I don't think the previous owner ever had it changed. (Maybe they did, but I have no records, so I'm assuming it is original.)
The engine is a 6.0 and the trans is the 4L80E.

I took my truck for a long drive the other day and I noticed that the transmission was slipping. It was an intermittent problem and did not seem to be load dependent.At one point I had cruise control on and when I noticed the slippage I tapped it down one without it locking, tapped it down once more, same thing, and finally, when I tapped it down a third time it locked up.Mind you, when it is locked I can give it about 1/3 throttle without it slipping, so it is not a matter of exceeding the holding ability.I tried putting it in third and it does the same thing, so I don't think it is the transmission, but the lockup clutch in the torque converter.The fluid looked okay, but I didn't get a really good look at it. The level is perfect.It is time to do a fluid change, since it has about 90,000 miles now, and I don't think the previous owner ever had it changed. (Maybe they did, but I have no records, so I'm assuming it is original.)The engine is a 6.0 and the trans is the 4L80E.

So, what do you think? Am I right? Is there an easy fix?

Sounds like a sticking TCC solenoid to me. You will need a scanner and a road test to be sure. That will tell if the PCM is outputting the lockup command, and if it's being applied or not.

When the TCC solenoid sticks does it fail to lock the converter altogether, or will it allow the converter to lock partway?

It could do many things, could stick open, could stick closed, or could stick partway, sometimes it won't release and the engine will stall as you come to a stop! I've got one doing that right now, my mom's 93 Pontiac GP. Pulled the TCC fuse and it's fine now so I'll just burn a chip and shut off the clutch, otherwise it will keep the SES light on. She never drives on the highway and never goes over 35 so this will be fine to shut off the clutch.